//翻转二叉树
public class TreeReverse {
}
class TreeReverseSolution{
    TreeNode reverseTree(TreeNode root){
        if(root==null)return null;
        TreeNode left = reverseTree(root.left);
        TreeNode right = reverseTree(root.right);
        root.left = right;
        root.right = left;
        return root;
    }
}